Japanese Unexamined Patent Application Publication No.2011-183271 (Patent Literature 1) is known as a background art in the technical field. The publication describes “the separator 30 has a magnetic drum configuration in which the magnetic group 34 is arranged close to the inner circumferential face of the drum rotor 32, the drum rotor 32 is integrated with the magnetic group 34 to rotate in the same direction as the flow direction of the raw water 38, and the scraping brush 52 is arranged at a position where the scraper 46 contacts the face of the drum rotor 32 (see abstract). However, the publication fails to disclose or suggest increasing (scaling up) treatment capability for the raw water with the magnetic drum configuration.